Put Your Hands Up for Intelligence

Ever wonder why people still “talk with their hands” when they’re on the telephone? We often use hand gestures while speaking even at times when the listener cannot see them. Gestures are processed in the same areas of the brain as speech (think sign language): the left inferior frontal gyrus (Broca’s) and the posterior middle temporal gyrus (Wenicke’s area). Hand movements help us to communicate more efficiently and emphasize certain points of the message we are trying to convey to our conversational partners. They’re an indication of our thought process throughout the discussion. Evolutionary insight proposes that the language brain regions, which originally supported the pairing of body language and meaning, have been adapted in humans for spoken language; however, we still don’t know precisely the reason why people gesture, and more interestingly, why some people use gestures more often than others.

A team of German researchers recently conducted a study suggesting a strong relationship between gesturing, fluid intelligence, and brain development. The scientists at Humboldt-Universität zu Berlin selected fifty-one 11th graders gifted in math and science for their experiment and separated them into groups of high and average fluid intelligence, which is responsible for learning and recognizing patterns. They asked both groups to solve analogy tasks that involved pairing sets of geometric configurations correctly. The students with higher fluid intelligence obviously performed better on the task than the students with average fluid intelligence, but they also produced more representational hand and arm gestures while describing how they solved the problems.

All of the students verbally explained the same method to solve the problems, but the students’ intelligence could be distinguished by simply observing their hand movements. The researchers considered that specifically the motion of hands rotating around an imaginary axis (a strategy that was never mentioned in the students’ accounts of the problems) was a reflection of mentally rotating the shapes and using spatial reasoning. Participants with higher fluid intelligence therefore engaged in more active mental representation during problem solving.

Furthermore, fMRI scans of the students’ brains showed that individuals with higher fluid intelligence and who had demonstrated more hand gestures showed greater cortical thickness in Broca’s areas and other areas in the left hemisphere such as the superior frontal cortex.

Both gesture and speech appear to be founded on the same underlying system of simulated action in mental imagery. We haven’t concluded whether gestures facilitate the development of fluid intelligence or whether the gestures themselves are its product. However, since young children are shown to gesture when learning new concepts and expressing new ideas, the activity may facilitate in cognitive development by simulating thought.